The types that matter for email
A and AAAA map a hostname to an IPv4 or IPv6 address. MX names the servers that accept your incoming mail. TXT holds arbitrary text and is where SPF, DMARC and DKIM live. CNAME aliases one hostname to another, which is how tracking domains and custom return-paths are usually wired. NS names the servers authoritative for your zone.
TTL and why it matters before a migration
Time To Live tells resolvers how long to cache a record. A 3600-second TTL means a change can take up to an hour to be seen everywhere; 86400 means up to a day.
The practical consequence: lower your TTLs before a migration, not during one. Drop them to 300 a day ahead, and the actual cutover propagates in minutes instead of hours. Doing it the other way round is how a planned ten-minute switch becomes a day of split delivery.
Propagation is caching, not travel
DNS changes do not spread outward from your server. They are published instantly at your authoritative nameservers, and the delay is entirely resolvers elsewhere serving cached copies until their TTL expires. This is why one person sees the new record and another does not, and why checking against several resolvers rather than one gives you the real picture.
Check yours
These run free in your browser. Nothing you type reaches a server.
Every record on this page starts at a registrar. Namecheap gives you free WHOIS privacy and a one-click switch of nameservers to Cloudflare, which is the setup I recommend for sending domains.
Get a domain at Namecheap →Affiliate link — it costs you nothing and helps keep this site free.Common questions
Why can I see my DNS change but someone else cannot?
Caching. Their resolver still holds the old record until its TTL expires. Nothing is wrong and nothing needs re-saving — it resolves itself.
What is split DNS?
When two sets of nameservers hold different records for the same domain, usually after a half-finished migration. Answers vary depending on which is queried, which produces intermittent failures that are very hard to diagnose.
Can one hostname have both a CNAME and other records?
No. A CNAME must be the only record at its name. This is why you cannot CNAME a root domain, and why providers offer ALIAS or ANAME records as a workaround.
Related concepts
If this is the thing going wrong
The pages explain it. If you would rather it was simply fixed, that is the work I do.